Phyllopod bed

The phyllopod bed is a 2.31 m thick layer of the 7 m thick Greater Phyllopod Bed,[4] found in the Walcott Quarry on Fossil Ridge, between Wapta Mountain and Mount Field, at an elevation of around 2,300 metres (7,500 ft), around 5 kilometres (3.1 mi) north of the railway town of Field, British Columbia, in the Canadian Rocky Mountains.

[8] Extensive quarrying was performed in field seasons until 1913, and Walcott considered the ton of shale he collected in his next visit, in 1917, to have practically exhausted the productive potential of the bed.

[7] There are (very rare) turbidite layers, but on the whole the unit was deposited in large events that dumped tens of centimetres of sediment at a time as a slurry of mud was washed over the site by a density current, sweeping up and entombing any organisms in its path.

[7] The preservation of the fossils – and their pre-burial livelihoods – was likely facilitated by mats of the cyanobacterium Morania, which served to bind the sediment and allow anoxic conditions to quickly form.

[9] Whilst trace fossils or ichnofauna are locally abundant in other areas of the Burgess Shale, they are almost completely absent in the Phyllopod bed,[10] perhaps as a result of the presence of Morania.